Abstract-Enhanced on-chip terahertz vibrational absorption spectroscopy using evanescent fields in silicon waveguide structures

 

Hadi Amarloo and Safieddin Safavi-Naeini

(a) Schematic of THz SBQ channel waveguide with sample holder [𝑤0$w_0$ = 180 𝜇$\mu$m, 𝑤$w$ = 5 mm, 𝐿$L$ = 8 mm]. (b) Simulation results for electric field distribution over the channel waveguide cross section at 532 GHz, the dashed lines show the boundaries of silicon. (c) Measurement setup [(1) network analyzer, (2) and (3) frequency extender modules, (4) and (5) rectangular metallic waveguide ports, (6) SBQ waveguide with sample holder filled by material under test]. (d) Measured transmission signal for the two cases of sample holder filled by polyethylene and 𝛼$\alpha$-lactose in arbitrary units.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-11-17343&id=451247

In this study, we demonstrate on-chip terahertz absorption spectroscopy using dielectric waveguide structures. The structures’ evanescent fields interact with the sample material surrounding the waveguide, enabling the absorption signature of the material to be captured. The ability of fabricated terahertz dielectric waveguide structures, based on the newly developed silicon-BCB-quartz platform, to capture the fingerprint of α-lactose powder (as an example material) at 532 GHz is examined. Enhancement of the spectroscopy sensitivity through techniques such as tapering the waveguide, confining the field in a slot dielectric waveguide, and increasing the interaction length using a spiral-shaped waveguide are investigated experimentally. The proposed on-chip spectroscopy structures outperform conventional and state-of-the-art approaches in terms of sensitivity and compactness.

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